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    <title>ShellCheck: SC3049 – In POSIX sh, using lower/mixed case for signal names is undefined.</title>
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    <h1>SC3049 – ShellCheck Wiki</h1>
    <a href="https://github.com/koalaman/shellcheck/wiki/SC3049">See this page on GitHub</a>
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    <h2
id="in-posix-sh-using-lowermixed-case-for-signal-names-is-undefined">In
POSIX sh, using lower/mixed case for signal names is undefined.</h2>
<h3 id="problematic-code">Problematic code:</h3>
<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="SC3049.html#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="bu">trap</span> <span class="st">&#39;handle_sigint&#39;</span> int</span></code></pre></div>
<h3 id="correct-code">Correct code:</h3>
<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="SC3049.html#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="bu">trap</span> <span class="st">&#39;handle_sigint&#39;</span> INT</span></code></pre></div>
<h3 id="rationale">Rationale:</h3>
<p>POSIX requires that signal names <a
href="https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_28">be
given in uppercase</a>:</p>
<blockquote>
<p>The condition can be EXIT, 0 (equivalent to EXIT), or a signal
specified using a symbolic name, without the SIG prefix, as listed in
the tables of signal names in the &lt;signal.h&gt; header defined in XBD
Headers; for example, HUP, INT, QUIT, TERM. Implementations may permit
names with the SIG prefix or ignore case in signal names as an
extension.</p>
</blockquote>
<h3 id="exceptions">Exceptions:</h3>
<p>None</p>
<h3 id="related-resources">Related resources:</h3>
<ul>
<li>Help by adding links to BashFAQ, StackOverflow, man pages, POSIX,
etc!</li>
</ul>
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